DETERMINATION OF CADMIUM IN BIOLOGICAL-MATERIALS BY FLAME ATOMIC-ABSORPTION SPECTROMETRY WITH FLOW-INJECTION ONLINE SORPTION PRECONCENTRATION

A new on-line preconcentration flame atomic absorption spectrometry (FAAS) system for trace element determination was developed based on sorption of soluble metal complexes on the walls of a PTFE knotted reactor using flow injection techniques. The system was applied to the determination of cadmium in biological materials. Cadmium complexed with sodium diethyldithiocarbamate was sorbed on the inner walls of the reactor and eluted on-line by isobutyl methyl ketone. The retention efficiency was 81% at a sampling loading rate of 5.2 ml/min. The enhancement factor was 66 and the concentration efficiency was 61/min with a 50 sec preconcentration period, consuming 4.2 ml sample. A detection limit of 0.1 mu g/l. Cd (3 sigma) was obtained with a sampling frequency of 55/hr. The precisions were 1.2% RSD for 20 mu g/l. Cd (N = 11). Thiourea and ascorbic acid/phenanthroline were used to overcome interferences from copper and iron, respectively. The analytical results obtained for powdered rice and human hair standard reference materials were in good agreement with the certified values.